Our long-term goal is to elucidate the relationship between neural activity, sound processing, perception and behavior. We specifically propose to establish the relationship of neural activity to discriminating and detecting sound features in the primary auditory cortex (A1) and lateral belt of non-human subjects with the goal of reveling the transformations occurring as the auditory cortical hierarchy is ascended. We address the question: How do neuronal responses in auditory cortex relate to non-human subjects' psychophysical and behavioral performance in detecting the presence of sound modulation? The three aims are designed to compare three fundamental aspects related to these issues in A1 and in two lateral belt areas of auditory cortex to determine the changing emphasis of processing along the ascending cortical pathway. Aim 1 is to determine the neural basis of modulation detection. Aim 2 is to determine how neuron responses from auditory cortex are related to perception and behavioral choices. Aim 3 is to determine the effect of behavioral state and task-engagement on neurons ability to encode sound features. To achieve these aims, we will establish the quantitative relationships between single unit auditory cortical activity and the ability of neurons and non-human subjects to discriminate sounds, and determine what codes most likely underlie perceptual ability. We will also record from single units while non-human subjects discriminate sound to determine the role of primary and secondary sensory cortical areas in the transformation from sensation to task performance. This will give insight into how active engagement in a task improves neural processing ability at the single neuron level and whether primary sensory cortex receives information or is involved in the processes that lead to action. Because the proposal relates brain function to different parts of the brain it is relevant for a better understanding about how punctate brain damage such as that cause by stroke affects auditory function. The results of these studies will help us to better understand how attending sound modulates auditory activity and thus makes this basic science have relevance for the spectrum disorders (that include, but are not limited to attention deficit disorder, dyslexia, etc). The results also could have relevance in helping to guide approaches to coding for hearing aids and cochlear implants since both neural coding and the ability to focus on sounds are relevant for designing these devices.